Add _PyThreadState_UncheckedGet()

Issue #26154: Add a new private _PyThreadState_UncheckedGet() function which
gets the current thread state, but don't call Py_FatalError() if it is NULL.

Python 3.5.1 removed the _PyThreadState_Current symbol from the Python C API to
no more expose complex and private atomic types. Atomic types depends on the
compiler or can even depend on compiler options. The new function
_PyThreadState_UncheckedGet() allows to get the variable value without having
to care of the exact implementation of atomic types.

Changes:

* Replace direct usage of the _PyThreadState_Current variable with a call to
  _PyThreadState_UncheckedGet().
* In pystate.c, replace direct usage of the _PyThreadState_Current variable
  with the PyThreadState_GET() macro for readability.
* Document also PyThreadState_Get() in pystate.h

1 files changed, 2 insertions, 4 deletions

diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 9a30fa8..8523511 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -1064,8 +1064,7 @@ PyDict_GetItem(PyObject *op, PyObject *key)
        Let's just hope that no exception occurs then...  This must be
        _PyThreadState_Current and not PyThreadState_GET() because in debug
        mode, the latter complains if tstate is NULL. */
-    tstate = (PyThreadState*)_Py_atomic_load_relaxed(
-        &_PyThreadState_Current);
+    tstate = _PyThreadState_UncheckedGet();
     if (tstate != NULL && tstate->curexc_type != NULL) {
         /* preserve the existing exception */
         PyObject *err_type, *err_value, *err_tb;
@@ -1102,8 +1101,7 @@ _PyDict_GetItem_KnownHash(PyObject *op, PyObject *key, Py_hash_t hash)
        Let's just hope that no exception occurs then...  This must be
        _PyThreadState_Current and not PyThreadState_GET() because in debug
        mode, the latter complains if tstate is NULL. */
-    tstate = (PyThreadState*)_Py_atomic_load_relaxed(
-        &_PyThreadState_Current);
+    tstate = _PyThreadState_UncheckedGet();
     if (tstate != NULL && tstate->curexc_type != NULL) {
         /* preserve the existing exception */
         PyObject *err_type, *err_value, *err_tb;